1. Field of the Invention
The present invention relates to a telecommunications network using an intelligent network (IN) architecture.
2. Related Art
The IN architecture has been developed to allow telecommunications networks to support services in a flexible and efficient manner. A fundamental feature of IN is the separation of call processing in a service switching point (SSP) from service control logic in a service control point (SCP). This separation allows the SSPs to be developed with a basic set of functions. To provide additional functions, control is passed out to an SCP at appropriate times during a call. The relevant service logic is then run at the SCP. The times at which control is passed to the SCP are known as detection points or DPs.
Conventionally, service switching functions (SSFs) have been carried out at the service switching point (SSP). The SSFs include the monitoring of the state of a call and when a detection point is reached checking with reference to a local trigger table to see if criteria appropriate to the detection point are met. If they are, then the SSF passes control to the service control point (SCP). The checking of call status against criteria appropriate to a given detection point is termed detection point processing.
According to a first aspect of the present invention, there is provided a method of operating a telecommunications intelligent network in which detection point processing for a call switched by a service switching point (SSP) is carried out at a service control point (SCP) remote from the SSP.
By contrast with the conventional approach in which all service switching functions (SSFs) have been carried out at the SSP, the present inventors have found that marked advantages are achieved by separating out the detection point processing and carrying out that part of the SSF at the service control point (SCP). This allows a process which is particularly computationally intensive to be run on a specialised platform. It also serves to weaken the association between a customer and a particular line at a given SSP. Typically a national network, such as the UK PSTN, might require many hundreds of local switches but possibly as few as four SCP""s. By storing the customer profile required for detection point processing centrally at the SCP""s, maintenance and updating of this data is greatly facilitated and service management is simplified. Since customer data need no longer be tied to a specific local switch, the invention helps to support customer mobility on a fixed network.
Preferably the method includes storing a trigger table for detection point processing distributed between the SCP and the SSP. Preferably all of the trigger table is stored initially at the SCP, and part of the trigger table is downloaded to the SSP when the cail switched by the SSP is initiated.
In the preferred implementation of the invention, a trigger table for use in detection point processing is distributed between the SSP and the SCP. It is particularly advantageous to store all of the table at the SCP, and to download data to the SSP only as required when a call is initiated. In this way, the link between a customer and a local switch is established dynamically and transiently for the duration of a call, and can readily be established at a different location for a subsequent call.
Preferably the method includes transmitting a request for detection point processing from the SSP to the SCP when during the progress of a call, a detection point occurs. Preferably the method includes storing data indicating the armed status of a detection point locally at the SSP, and the said step of transmitting a request for DP processing from the SSP to the SCP is carried out only for those detection points which are armed.
In this preferred approach to implementing the invention, while substantially all DP processing is carried out remotely, information on whether each DP is armed is made available locally at the SSP, for example by downloading that part of the trigger table which carries this data when the call is initiated. This has the effect of reducing the amount of signalling necessary between the SSP and the SCP.
Preferably the said step of storing data includes storing arming type information indicating whether the DP is of a request or notification type, and the method includes suspending processing of a call when an armed DP is encountered only if the DP is of the request type.
The efficiency of operation of the system is further enhanced if in addition the service switching point stores DP arming type information locally. This ensures that local processing of the call is suspended only when necessary, that is when the detection point is of the request type. Preferably this approach is implemented by providing a trigger table which is distributed between SCP nd the SSP. The trigger table in the SCP will then contain the data necessary for DP processing, whilst the table in the SSP retains the data necessary for identifying armed DPs and call suspension criteria.
According to a second aspect of the present invention, there is provided a telecommunications intelligent network comprising:
a service switching point (SSP); and
a service control point (SCP) which is remote from the SSP and which includes detection point processing means for processing a call switched by the SSP.
The invention also encompasses a service control point and a method of operating a service control point.